The hormone angiotensin II has several prominent effects on body fluid homeostasis which are mediated by receptors within the central nervous system. It is known that intracranial injection of the hormone into the cerebral ventricles or infusion into the circulation causes elevated water intake. One identified site of dipsogenic action of angiotensin is the subfornical organ (SFO), one of the circumventricular organs of the brain. Recent data have also indicated that the organum vasculosum of the lamina terminalis (OVLT) is another potential behavioral site of action of angiotensin. The proposed experiments will evaluate this latter hypothesis. The interaction between receptors for angiotensin at the SFO and at the OVLT will be studied. A thorough analysis of the neuropharmacology of angiotensin-induced drinking at the subfornical organ will be performed. Finally, initial data will be obtained on the role of the SFO in hydromineral excretion. Thus, information concerning the neuroanatomical localization of brain angiotensin receptors will be obtained, and a more thorough understanding of the role of this hormone in the control of behavior will be possible. In addition, the functional role of two of the circumventricular organs of the brain will be studied.